"I don't know. Do you not have very many kinds of animals? Since there's no combinatorial explosion?"

"We have a lot of animals. We have I think several million kinds of beetle, thousands upon thousands of kinds of birds, mammals, reptiles, uncountable sea creatures...I'm not a taxonomist or I'd have better figures but it's a lot."

"...Okay. Maybe you have more kinds of animals than we do. Since instead of crossing and generalizing they're specializing ever-finer until you have millions of kinds of beetle."

"Probably, yeah. I'm not the best person to ask, evolution isn't my field of study."

"Fair enough. ...That is so many beetles. Counting everything that has as a component any kind of beetle we probably have a few thousand, it's a good design, but that's just ridiculous."

"I think beetles are one of the more numerous kinds of animal on the planet, yeah."

"Rocs are an unusually streamlined animal. I think they're eagle/ospreys but they're one of the animals that gets their own name."

"Well, they're a specific thing in my world's mythology. I think the fictional version eats elephants or something."

"I mean, rocs are big enough that they could probably eat most of an elephant-rat, maybe even an elephant-rhino if they took their time, but they prefer fish."

"...Rats are tiny. Rhinos are not tiny but significantly smaller than an elephant. I suspect that elephant-rats and elephant-rhinos are smaller than just plain elephants."

"I don't actually know how big any of these things are as isolates. An elephant-rat is yea big -" She gestures a size that's a bit bigger than a regular rat. "I say 'most of' because it wouldn't have fish bones and the roc wouldn't be able to swallow it whole, it wouldn't be much of a meal really... An elephant-rhino is huge, though."

"Hey, Bar, can we have pictures of an elephant and an elephant-rhino on approximately the same scale?"

They can get a spread of all the elephant crosses, including the elephant koi, which is the biggest. The elephant-rhino is second-biggest, about the size of an Earth elephant.

"Okay, that's about the size of an Asian elephant. African elephants are bigger, but I don't remember which one rocs were supposed to eat, so."

"I couldn't tell you."

"Bar?"

The mythology is not quite clear.

"Well, fair enough, mythology does that sometimes."

"Oh well."

"She sounds nice, anyway, I have a friend who has wings and he took me up once instead of my going under my own power. It was different."

"I like having a roc. The traditional Air Avatar animal companion is a flying bison but they're a nightmare to keep and feed in an urban environment. A trained roc can be half-wild and still take passengers."

"How does a bison fly? Are they a cross with some kind of bird or bat or something?"

"No, flying bison are actually crossed with manatees; they fly with airbending. There's one kind of animal that can do each kind of bending except for some reason waterbending - I guess you could count the sacred koi as 'doing waterbending' but really they don't."

"What are the sacred koi?"

"There are two koi in a pool at the North Pole who represent the moon spirit and the ocean spirit. But the actual fish don't do any bending, they just swim in a circle."